Climate variability outweighs influence of climate mean on summer precipitation extremes

Climate change can involve changes in mean conditions, and in their variability on short to long timescales. But which of the two  is more important for our future climate?  We present a study indicating that for the number of extreme precipitation days, changes in climate variability dominate over  changes in the mean state. This analysis is based on three large ensemble simulations across three CMIP6 models (MPI-ESM1-2-LR, CanESM5, and ACCESS-ESM1-5). Here, we decompose the total changes in daily summer precipitation and daily maximum temperature into mean and variability components (standard deviation and skewness of the daily probability density functions).  Our key findings are that:1) Changes in climate variability (i.e., day-to-day variability of precipitation and changes in the precipitation distribution) have a more pronounced impact on extreme precipitation events than changes in the mean state. 2) In contrast, changes in the mean temperature state play a more dominant role in determining overall changes in daily temperature. These insights  are valuable for understanding the mechanisms driving extreme weather events and  highlight the need to consider daily variability changes in climate change impact assessments.